Electronic Devices with Multiple Energy Storage Device Charging Circuits and Corresponding Methods

ABSTRACT

An electronic device included a first energy storage device coupled to a second energy storage device by a conductor. A charging node is coupled to the first energy storage device. Another conductor couples the charging node to the second energy storage device. A switch is electrically coupled between the conductor and the second energy storage device. A control circuit opens the switch, thereby allowing a first charging current to flow from the charging node to the first energy storage device through the conductor and a second charging current to flow from the charging node to the second energy storage device through the other conductor and closes the switch when a difference between a voltage of the first energy storage device and a voltage of the second energy storage device is within a predefined voltage difference threshold.

BACKGROUND Technical Field

This disclosure relates generally to electronic devices, and moreparticularly to electronic devices having multiple energy storagedevices.

Background Art

Portable electronic devices such as smartphones, laptop computers,tablet computers, and two-way radios derive their portability fromenergy storage devices, one example of which is a rechargeableelectrochemical cell. In some situations, an electronic device willinclude two or more rechargeable cells that are coupled together inserial or in parallel. When the energy stored within the rechargeablecells becomes depleted, it is necessary to attach a power supply to theelectronic device to recharge the cells.

Where circuit impedances between the rechargeable cells is non-trivial,such impedances can cause voltage drops during charging that effectivelyderate the maximum usable capacity from the overall energy storagesystem. In some situations, minimizing these circuit impedances isdifficult due to the physical constraints associated with a design for aparticular application. It would be advantageous to have improvedcharging circuits for electronic devices having multiple energy storagedevices, as well as methods of charging these energy storage devices,that reduce these adverse effects on charging performance.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying figures, where like reference numerals refer toidentical or functionally similar elements throughout the separate viewsand which together with the detailed description below are incorporatedin and form part of the specification, serve to further illustratevarious embodiments and to explain various principles and advantages allin accordance with the present disclosure.

FIG. 1 illustrates one explanatory electronic device in accordance withone or more embodiments of the disclosure.

FIG. 2 illustrates a perspective view of one explanatory electronicdevice in accordance with one or more embodiments of the disclosure in aclosed position.

FIG. 3 illustrates a side elevation view of one explanatory electronicdevice in accordance with one or more embodiments of the disclosure in apartially open position.

FIG. 4 illustrates a side elevation view of one explanatory electronicdevice in accordance with one or more embodiments of the disclosure inan axially displaced open position.

FIG. 5 illustrates an exploded view of one explanatory electronic devicein accordance with one or more embodiments of the disclosure in theaxially displaced open position.

FIG. 6 illustrates one explanatory circuit in accordance with one ormore embodiments of the disclosure.

FIG. 7 illustrates one explanatory substrate supporting one or moreelectrical conductors in accordance with one or more embodiments of thedisclosure.

FIG. 8 illustrates another explanatory circuit in accordance with one ormore embodiments of the disclosure.

FIG. 9 illustrates one explanatory method in accordance with one or moreembodiments of the disclosure.

FIG. 10 illustrates still another explanatory circuit in accordance withone or more embodiments of the disclosure.

FIG. 11 illustrates another explanatory method in accordance with one ormore embodiments of the disclosure.

FIG. 12 illustrates various embodiments of the disclosure.

Skilled artisans will appreciate that elements in the figures areillustrated for simplicity and clarity and have not necessarily beendrawn to scale. For example, the dimensions of some of the elements inthe figures may be exaggerated relative to other elements to help toimprove understanding of embodiments of the present disclosure.

DETAILED DESCRIPTION OF THE DRAWINGS

Before describing in detail embodiments that are in accordance with thepresent disclosure, it should be observed that the embodiments resideprimarily in combinations of method steps and apparatus componentsrelated to charging multiple energy storage devices, one example ofwhich is an electrochemical cell, situated in an electronic device. Anyprocess descriptions or blocks in flow charts should be understood asrepresenting modules, segments, or portions of code that include one ormore executable instructions for implementing specific logical functionsor steps in the process.

Alternate implementations are included, and it will be clear thatfunctions may be executed out of order from that shown or discussed,including substantially concurrently or in reverse order, depending onthe functionality involved. Accordingly, the apparatus components andmethod steps have been represented where appropriate by conventionalsymbols in the drawings, showing only those specific details that arepertinent to understanding the embodiments of the present disclosure soas not to obscure the disclosure with details that will be readilyapparent to those of ordinary skill in the art having the benefit of thedescription herein.

Embodiments of the disclosure do not recite the implementation of anycommonplace business method aimed at processing business information,nor do they apply a known business process to the particulartechnological environment of the Internet. Moreover, embodiments of thedisclosure do not create or alter contractual relations using genericcomputer functions and conventional network operations. Quite to thecontrary, embodiments of the disclosure employ methods that, whenapplied to electronic device and/or charging technology, improve thefunctioning of the electronic device itself by and improving theperformance that can be achieved from a multiple energy storage devicesystem in which non-zero impedances occur in circuit components couplingone energy storage device to another.

It will be appreciated that embodiments of the disclosure describedherein may be comprised of one or more conventional processors andunique stored program instructions that control the one or moreprocessors to implement, in conjunction with certain non-processorcircuits, some, most, or all of the functions of opening a switchelectrically coupled between a conductor coupling a first energy storagedevice to a second energy storage device and one of the energy storagedevices while a difference between the voltages of the first energystorage device and the second energy storage device exceeds a thresholdto temporarily charge the first energy storage device and the secondenergy storage in parallel as described herein. The non-processorcircuits may include, but are not limited to, a control circuit,switches, overprotection circuits, fuel gauging circuits, diodes, signaldrivers, clock circuits, power source circuits, and user input devices.As such, these functions may be interpreted as steps of a method toperform opening a switch coupled between a first energy storage deviceand a second energy storage device when the difference between thevoltage of the first energy storage device and the second energy storagedevice exceeds a predefined voltage difference threshold, therebyallowing a first charging current to flow from a charging node throughan electrical conductor to the first energy storage device while asecond charging current flows from the charging node through anotherelectrical conductor to the second energy storage device. Alternatively,some or all functions could be implemented by a state machine that hasno stored program instructions, or in one or more application specificintegrated circuits (ASICs), in which each function or some combinationsof certain of the functions are implemented as custom logic. Of course,a combination of the two approaches could be used.

Thus, methods and means for these functions have been described herein.Further, it is expected that one of ordinary skill, notwithstandingpossibly significant effort and many design choices motivated by, forexample, available time, current technology, and economicconsiderations, when guided by the concepts and principles disclosedherein will be readily capable of generating such software instructionsand programs and ASICs with minimal experimentation.

Embodiments of the disclosure are now described in detail. Referring tothe drawings, like numbers indicate like parts throughout the views. Asused in the description herein and throughout the claims, the followingterms take the meanings explicitly associated herein, unless the contextclearly dictates otherwise: the meaning of “a,” “an,” and “the” includesplural reference, the meaning of “in” includes “in” and “on.” Relationalterms such as first and second, top and bottom, and the like may be usedsolely to distinguish one entity or action from another entity or actionwithout necessarily requiring or implying any actual such relationshipor order between such entities or actions.

As used herein, components may be “operatively coupled” when informationcan be sent between such components, even though there may be one ormore intermediate or intervening components between, or along theconnection path. The terms “substantially,” “essentially,”“approximately,” “about” or any other version thereof, are defined asbeing close to as understood by one of ordinary skill in the art, and inone non-limiting embodiment the term is defined to be within tenpercent, in another embodiment within five percent, in anotherembodiment within one percent and in another embodiment within one-halfpercent. The term “coupled” as used herein is defined as connected,although not necessarily directly and not necessarily mechanically.Also, reference designators shown herein in parenthesis indicatecomponents shown in a figure other than the one in discussion. Forexample, talking about a device (10) while discussing figure A wouldrefer to an element, 10, shown in figure other than figure A.

Embodiments of the disclosure provide circuits and methods for chargingelectronic devices having multiple energy storage devices situatedtherein. In one or more embodiments, and electronic device comprises afirst energy storage device coupled to a second energy storage device bya conductor. In one or more embodiments, the conductor has a non-trivialimpedance associated therewith. For instance, in an explanatoryembodiment used below for illustration purposes, the electronic deviceincludes a first device housing coupled to a second device housing by ahinge such that the first device housing is pivotable about the hingerelative to the second device housing between an axially displaced openposition and a closed position. In one or more embodiments, the firstenergy storage device is situated in the first device housing, while thesecond energy storage device is situated in the second device housing. Aflexible conductor then spans the hinge and couples the first energystorage device and the second energy storage device in parallel so thatthey function as a singular energy storage device having an increasedcurrent capacity as a result of the parallel configuration.

In one or more embodiments, a charging node is coupled to the firstenergy storage device. Another conductor, which may be configured asanother electrically conductive trace along the flexible substrate,couples the charging node to the second energy storage device.

In one or more embodiments, a switch is electrically coupled between theconductor coupling the first energy storage device and the second energystorage device and the second energy storage device itself. Opening theswitch allows the connection provided by the conductor to beinterrupted.

In one or more embodiments, a control circuit opens the switch when adifference between a voltage of the first energy storage device andanother voltage of the second energy storage device exceeds a predefinedvoltage difference threshold. This allows the first energy storagedevice to be charged with current flowing from the charging node throughthe conductor, while the second energy storage device is charged withcurrent flowing from the charging node through the other conductor.Thereafter, the control circuit closes the switch when the differencebetween the voltage of the first energy storage device and the voltageof the second energy storage device is within the predefined voltagedifference threshold.

To allow cell balancing while the switch is opened, in one or moreembodiments a current limiting conductor is coupled in parallel with theswitch. In one or more embodiments, the current limiting conductorcomprises a resistor coupled in parallel with the switch. In otherembodiments, the current limiting conductor comprises a resistor coupledin series with another switch, with that serial combination beingcoupled in parallel with the first switch. In one or more embodiments,the control circuit can close the other switch when the differencebetween the voltage of the first energy storage device and the voltageof the second energy storage device exceeds the predefined voltagedifference threshold and/or when the first switch is open. Thisadvantageously allows the voltage of the first energy storage device andthe voltage of the second energy storage device to come to equilibriumin a controlled manner.

Accordingly, embodiments of the disclosure provide a method of opening aswitch coupled between a first energy storage device and an electricalconductor coupling the switch to a second energy storage device when adifference between a voltage of the first energy storage device and avoltage of the second energy storage device exceeds a predefined voltagedifference threshold, thereby allowing a first charging current to flowfrom a charging node to the first energy storage device while a secondcharging current flows from the charging node to the second energystorage device through another conductor. When implemented in anelectronic device having a first device housing coupled to a seconddevice housing by a hinge, with the first energy storage device situatedin the first device housing and the second energy storage devicesituated in the second device housing, a control circuit can open theswitch when the difference between the voltage of the first energystorage device and the voltage of the second energy storage deviceexceeds the predefined voltage difference threshold, and then close theswitch when the difference between the voltage of the first energystorage device and the voltage of the second energy storage device fallswithin the predefined voltage difference threshold.

Advantageously, embodiments of the disclosure allow the maximum chargecurrent (as specified for each energy storage device) to be delivered toeach energy storage device during charging. The net result is fastercharging and a better user experience.

Turning now to FIG. 1, illustrated therein is one explanatory electronicdevice 100 configured in accordance with one or more embodiments of thedisclosure. The electronic device 100 of FIG. 1 is a portable electronicdevice. For illustrative purposes, the electronic device 100 is shown asa smartphone. However, the electronic device 100 could be any number ofother devices as well, including tablet computers, gaming devices,multimedia players, and so forth. Still other types of electronicdevices can be configured in accordance with one or more embodiments ofthe disclosure as will be readily appreciated by those of ordinary skillin the art having the benefit of this disclosure.

The electronic device 100 could take any of a variety of shapes. Forexplanatory purposes, the electronic device 100 is illustrated as adeformable electronic device having a first device housing 102 and asecond device housing 103 coupled together by a hinge 101. Thisconstruct is used for explanatory purposes herein because it provides anillustration of how an electrical conductor spanning the hinge caninclude higher impedances between circuit components, e.g.,electrochemical cells, than may occur in other circuit configurations.For instance, when a first rechargeable cell is situated within thefirst device housing 102, with a second rechargeable cell situated inthe second device housing 103, an electrical conductor spanning thehinge 101 to couple these rechargeable cells together may include animpedance that is on the order of milli-Ohms. When this occurs, anyvoltage drop across this impedance essentially derates the maximumusable capacity from the overall battery system defined by therechargeable cells. While a deformable device is one explanatorysituation in which design constraints may preclude simply using aconductor with a lower impedance, others will be obvious to those ofordinary skill in the art having the benefit of this disclosure.Accordingly, the electronic device 100 of FIG. 1 is illustrative only.

In one or more embodiments, a hinge 101 couples the first device housing102 to the second device housing 103. In one or more embodiments, thefirst device housing 102 is selectively pivotable about the hinge 101relative to the second device housing 103. For example, in one or moreembodiments the first device housing 102 is selectively pivotable aboutthe hinge 101 between a closed position, shown and described below withreference to FIG. 2, and an axially displaced open position, shown inFIG. 1 and described below with reference to FIG. 4.

In one or more embodiments the first device housing 102 and the seconddevice housing 103 are manufactured from a rigid material such as arigid thermoplastic, metal, or composite material, although othermaterials can be used. Still other constructs will be obvious to thoseof ordinary skill in the art having the benefit of this disclosure.

In the illustrative embodiment of FIG. 1, the electronic device 100includes a single hinge. However, in other embodiments two or morehinges can be incorporated into the electronic device 100 to allow it tobe folded in multiple locations.

This illustrative electronic device 100 of FIG. 1 includes a display105. The display 105 can optionally be touch-sensitive. In oneembodiment where the display 105 is touch-sensitive, the display 105 canserve as a primary user interface of the electronic device 100. Userscan deliver user input to the display 105 of such an embodiment bydelivering touch input from a finger, stylus, or other objects disposedproximately with the display 105.

In one embodiment, the display 105 is configured as an organic lightemitting diode (OLED) display fabricated on a flexible plasticsubstrate, thereby making the display 105 a flexible display 105. Thisallows the display 105 to be flexible so as to deform when the firstdevice housing 102 pivots about the hinge 101 relative to the seconddevice housing 103. However, it should be noted that other types ofdisplays suitable for use with the electronic device 100 will be obviousto those of ordinary skill in the art having the benefit of thisdisclosure. Illustrating by example, in other embodiments multipledisplays can be used. For instance, a first rigid display can be coupledto the first device housing 102, while a second, separate rigid displaycan be coupled to the second device housing 103, with the hinge 101separating the two displays.

Features can be incorporated into the first device housing 102 and/orthe second device housing 103. Examples of such features include acamera 106 or an optional speaker port 107, which are shown disposed onthe rear side of the electronic device 100 in this embodiment but couldbe placed on the front side as well. In this illustrative embodiment, auser interface component 108, which may be a button or touch sensitivesurface, can also be disposed along the rear side of the first devicehousing 102. As noted, any of these features are shown being disposed onthe rear side of the electronic device 100 in this embodiment, but couldbe located elsewhere, such as on the front side in other embodiments. Inother embodiments, these features may be omitted.

A block diagram schematic 110 of the electronic device 100 is also shownin FIG. 1. The block diagram schematic 110 can be configured as aprinted circuit board assembly disposed within either or both of thefirst device housing 102 or the second device housing 103 of theelectronic device 100. Various components can be electrically coupledtogether by conductors or a bus disposed along one or more printedcircuit boards. For example, as will be described below with referenceto FIG. 6, some components of the block diagram schematic 110 can beconfigured as a first electronic circuit fixedly situated within thefirst device housing 102, while other components of the block diagramschematic 110 can be configured as a second electronic circuit fixedlysituated within the second device housing 103. As will be described inmore detail below with reference to FIGS. 5 and 7, a flexible substratecan then span the hinge 101 to electrically couple the first electroniccircuit to the second electronic circuit.

In one or more embodiments, the electronic device 100 includes one ormore processors 112. In one embodiment, the one or more processors 112can include an application processor and, optionally, one or moreauxiliary processors. One or both of the application processor or theauxiliary processor(s) can include one or more processors. One or bothof the application processor or the auxiliary processor(s) can be amicroprocessor, a group of processing components, one or more ASICs,programmable logic, or other type of processing device.

The application processor and the auxiliary processor(s) can be operablewith the various components of the electronic device 100. Each of theapplication processor and the auxiliary processor(s) can be configuredto process and execute executable software code to perform the variousfunctions of the electronic device 100. A storage device, such as memory113, can optionally store the executable software code used by the oneor more processors 112 during operation.

In this illustrative embodiment, the electronic device 100 also includesa communication circuit 114 that can be configured for wired or wirelesscommunication with one or more other devices or networks. The networkscan include a wide area network, a local area network, and/or personalarea network. The communication circuit 114 may also utilize wirelesstechnology for communication, such as, but are not limited to,peer-to-peer or ad hoc communications such as HomeRF, Bluetooth and IEEE802.11, and other forms of wireless communication such as infraredtechnology. The communication circuit 114 can include wirelesscommunication circuitry, one of a receiver, a transmitter, ortransceiver, and one or more antennas 115.

In one embodiment, the one or more processors 112 can be responsible forperforming the primary functions of the electronic device 100. Forexample, in one embodiment the one or more processors 112 comprise oneor more circuits operable with one or more user interface devices, whichcan include the display 105, to present, images, video, or otherpresentation information to a user. The executable software code used bythe one or more processors 112 can be configured as one or more modules116 that are operable with the one or more processors 112. Such modules116 can store instructions, control algorithms, logic steps, and soforth.

In one embodiment, the one or more processors 112 are responsible forrunning the operating system environment of the electronic device 100.The operating system environment can include a kernel and one or moredrivers, and an application service layer, and an application layer. Theoperating system environment can be configured as executable codeoperating on one or more processors or control circuits of theelectronic device 100. The application layer can be responsible forexecuting application service modules. The application service modulesmay support one or more applications or “apps.” The applications of theapplication layer can be configured as clients of the applicationservice layer to communicate with services through application programinterfaces (APIs), messages, events, or other inter-processcommunication interfaces. Where auxiliary processors are used, they canbe used to execute input/output functions, actuate user feedbackdevices, and so forth.

In one embodiment, the electronic device 100 optionally includes one ormore flex sensors 104, operable with the one or more processors 112, todetect a bending operation that causes the first device housing 102 topivot about the hinge 101 relative to the second device housing 103,thereby transforming the electronic device 100 into a deformed geometry,such as that shown in FIGS. 2-3. The inclusion of flex sensors 104 isoptional, and in some embodiment flex sensors 104 will not be included.

In one embodiment, the one or more processors 112 may generate commandsor execute control operations based on information received from thevarious sensors, including the one or more flex sensors 104, the userinterface, or the other sensors 109. The one or more processors 112 mayalso generate commands or execute control operations based uponinformation received from a combination of the one or more flex sensors104, the user interface, or the other sensors 109. Alternatively, theone or more processors 112 can generate commands or execute controloperations based upon information received from the one or more flexsensors 104 or the user interface alone. Moreover, the one or moreprocessors 112 may process the received information alone or incombination with other data, such as the information stored in thememory 113.

The one or more other sensors 109 may include a microphone, an earpiecespeaker, a second loudspeaker (disposed beneath speaker port 107), and auser interface component such as a button or touch-sensitive surface.The one or more other sensors 109 may also include key selectionsensors, proximity sensors, a touch pad sensor, a touch screen sensor, acapacitive touch sensor, and one or more switches. Touch sensors may beused to indicate whether any of the user actuation targets present onthe display 105 are being actuated. Alternatively, touch sensorsdisposed in the electronic device 100 can be used to determine whetherthe electronic device 100 is being touched at side edges or major facesof the first device housing 102 or the second device housing 103. Thetouch sensors can include surface and/or housing capacitive sensors inone embodiment. The other sensors 109 can also include audio sensors andvideo sensors (such as a camera).

The other sensors 109 can also include motion detectors, such as one ormore accelerometers or gyroscopes. For example, an accelerometer may beembedded in the electronic circuitry of the electronic device 100 toshow vertical orientation, constant tilt and/or whether the electronicdevice 100 is stationary. A gyroscope can be used in a similar fashion.

Other components 111 operable with the one or more processors 112 caninclude output components such as video outputs, audio outputs, and/ormechanical outputs. Examples of output components include audio outputssuch as speaker port 107, earpiece speaker, or other alarms and/orbuzzers and/or a mechanical output component such as vibrating ormotion-based mechanisms. Still other components will be obvious to thoseof ordinary skill in the art having the benefit of this disclosure.

In one or more embodiments, the electronic device 100 comprises a firstenergy storage device 118 and a second energy storage device 119. Thefirst energy storage device 118 and the second energy storage device 119can take a variety of forms. In an illustrative embodiment shown belowin FIG. 6, the first energy storage device 118 and the second energystorage device 119 each comprise electrochemical cells. For instance,the first energy storage device 118 and the second energy storage device119 can each comprise a lithium-ion, lithium-polymer, or other type ofrechargeable cell. Other examples of energy storage devices suitable foruse with embodiments of the disclosure will be obvious to those ofordinary skill in the art having the benefit of this disclosure. Forinstance, in other embodiments the first energy storage device 118 andthe second energy storage device 119 may be a supercapacitor, and soforth.

In one or more embodiments, the first energy storage device 118 issituated within the first device housing 102, while the second energystorage device 119 is situated within the second device housing 103. Inone or more embodiments, an electrical conductor (one example of whichis illustrated and described below with reference to FIG. 7) couples thefirst energy storage device 118 to the second energy storage device 119.

Charging circuitry 117 can be included to selectively charge the firstenergy storage device 118 and the second energy storage device 119 whendepleted. In one or more embodiments, the charging circuitry 117comprises a charging node 120 that is coupled to the first energystorage device 118. In one or more embodiments, the charging circuitryalso includes another conductor coupling the charging node 120 to thesecond energy storage device 119.

In one or more embodiments, the charging circuitry 117 includes a switchthat is electrically coupled between the conductor coupling the firstenergy storage device 118 to the second energy storage device 119 andthe second energy storage device 119. Opening the switch disconnects theconductor from the second energy storage device 119, while closing theswitch couples, in one or more embodiments, the cathode of the firstenergy storage device 118 to the cathode of the second energy storagedevice 119.

In one or more embodiments, a control circuit 124 is then operable toopen the switch when a difference between a voltage of the first energystorage device 118 and a voltage of the second energy storage device 119exceeds a predefined voltage difference threshold. In one or moreembodiments, the control circuit 124 is operable to close the switchwhen the difference between the voltage of the first energy storagedevice 118 and the voltage of the second energy storage device 119 iswithin the predefined voltage difference threshold. The operation of theswitch and the control circuit 124 will be described in more detailbelow with reference to FIG. 8.

It is to be understood that FIG. 1 is provided for illustrative purposesonly and for illustrating components of one electronic device 100 inaccordance with embodiments of the disclosure and is not intended to bea complete schematic diagram of the various components required for anelectronic device. Therefore, other electronic devices in accordancewith embodiments of the disclosure may include various other componentsnot shown in FIG. 1 or may include a combination of two or morecomponents or a division of a particular component into two or moreseparate components, and still be within the scope of the presentdisclosure.

Turning now to FIG. 2, illustrated therein is the electronic device 100in a closed state. In this state, the first device housing 102 has beenpivoted about the hinge 101 toward the second device housing 103 to aclosed position 200. When in the closed position 200, a front surface202 of the first device housing 102 abuts a front surface 203 of thesecond device housing 103.

In this illustrative embodiment, a hinge housing 201 comprising thehinge 101 is revealed when the electronic device 100 is in the closedposition 200. In other embodiments, the hinge housing 201 will remainconcealed when the first device housing 102 pivots about the hinge 101relative to the second device housing 103 to the closed position 200.Effectively, in either embodiment, the first device housing 102 and thesecond device housing 103 are analogous to clam shells that have beenshut by the claim, thereby giving rise to the “clamshell” style ofdevice. When the clamshell opens, the display (105) is revealed.

In some embodiments, features can be included to further retain theelectronic device 100 in the closed position 200. Illustrating byexample, in one embodiment a mechanical latch can be included to retainthe first device housing 102 and the second device housing 103 in theclosed position 200. In other embodiments, magnets can be incorporatedinto the front surface 202 of the first device housing 102 and the frontsurface 203 of the second device housing 103 to retain the first devicehousing 102 and the second device housing 103 in the closed position200.

In still other embodiments, frictional elements can be incorporated intothe hinge 101 to retain the first device housing 102 and the seconddevice housing 103 in a particular position. A stator motor could beintegrated into the hinge 101 to perform this function as well. In otherembodiments torsion springs used in combination with a cam havingmechanical detents and a stator with mechanical protrusions are used toperform this function. Still other mechanical structures and devicessuitable for retaining the electronic device 100 in the closed position200 will be obvious to those of ordinary skill in the art having thebenefit of this disclosure.

Turning now to FIG. 3, the electronic device 100 is shown beingtransitioned from the closed position (200) of FIG. 2 to a partiallyopen position 300. Specifically, the first device housing 102 ispivoting about the hinge 101 away from the second device housing 103toward an open position. The open position 300 shown in FIG. 3 is a“tent position.” In the side elevation view of FIG. 3, the hinge housing201 is exposed between the first device housing 102 and the seconddevice housing 103.

Turning now to FIG. 4, illustrated therein is the electronic device 100in an axially displaced open position 400. In the axially displaced openposition 400, the first device housing 102 is rotated about the hinge101 so as to be axially displaced 180-degrees out of phase with thesecond device housing 103, thereby revealing the display (105). In thisillustrative embodiment, this causes the hinge housing (201) to beconcealed within the first device housing 102 and second device housing103.

In such a configuration, the first device housing 102 and the seconddevice housing 103 effectively define a plane. Since this illustrativeembodiment includes a flexible display, the flexible display has beenelongated into a flat position.

Turning now to FIG. 5, illustrated therein is an exploded view of theelectronic device 100. This view of the electronic device 100 allowsvarious components of the first device housing 102, the second devicehousing 103, and the hinge 101 to be more clearly seen due to the factthat the display 105 and other components have been detached from thefirst device housing 102 and the second device housing 103 and shown inan exploded format.

As shown in FIG. 5, the display 105 is situated beneath a flexiblefascia 501, which serves as a protective layer for the display 105. Thedisplay 105 and the flexible fascia 501 can be coupled to the firstdevice housing 102 and the second device housing 103 so as to span thehinge 101. This allows the display 105 and flexible fascia 501 to deformwhen the first device housing 102 pivots about the hinge 101 relative tothe second device housing 103.

Also shown in FIG. 5 is the flexible substrate 502. In one or moreembodiments, the flexible substrate 502 provides a reliable electricallink through the hinge 101 between a first electronic circuit 503disposed in the first device housing 102 and a second electronic circuit504 disposed in the second device housing 103. In one or moreembodiments, the flexible substrate 502 spans the hinge to couple thefirst electronic circuit 503 to the second electronic circuit 504.

Turning now to FIG. 6, illustrated therein is a schematic diagram 600illustrating further details of one example the first electronic circuit503 and the second electronic circuit 504. As shown, the flexiblesubstrate 502 electrically couples the first electronic circuit 503 tothe second electronic circuit 504. Power (voltage and current), digitalsignals, analog signals, common nodes (e.g., ground or Vcc), and otherelectrical connections can be coupled between the first electroniccircuit 503 and the second electronic circuit 504 via the flexiblesubstrate 502.

In one or more embodiments, each of the first electronic circuit 503 andthe second electronic circuit 504 includes load elements 601,602 thatcan be configured as one or more electrical components, e.g., resistors,capacitors, inductors, integrated circuit chips, and so forth. In one ormore embodiments, these load elements 601,602 can be coupled to one ormore printed circuit boards or other substrates so as to form a printedcircuit board assembly. The load elements 601,602 can include the someof the elements described above with reference to FIG. 1, such as theone or more processors (112), the memory (113), the communicationcircuit (114), the other components 111, and so forth.

The first electronic circuit 503 can include a first circuit board,while the second electronic circuit 504 can include a second circuitboard, and so forth. In one embodiment, each of the first circuit boardand the second circuit board can be manufactured from multiple layers.Some layers can comprise selectively placed conductive metal, such ascopper or aluminum, while other layers can be insulative. Insulativelayers can be manufactured from fiberglass, FR4, or other materials. Inone or more embodiments, each of the first circuit board and the secondcircuit board comprises a fiberglass printed circuit board. In anotherembodiment, each of the first circuit board and the second circuit boardis a FR4 printed circuit board.

In one or more embodiments, the first electronic circuit 503 comprises afirst energy storage device 118, while the second electronic circuit 504comprises a second energy storage device 119. In this illustrativeembodiment, the first energy storage device 118 and the second energystorage device 119 each comprise rechargeable electrochemical cells. Inone or more embodiments, the rechargeable electrochemical cells arelithium-based cells, such as lithium-ion or lithium-polymer cells. Otherexamples of both energy storage devices and rechargeable electrochemicalcells will be obvious to those of ordinary skill in the art having thebenefit of this disclosure.

Other components can be included to manage the charging and dischargingof the first energy storage device 118 and the second energy storagedevice 119 in one or more embodiments. Illustrating by example, in oneor more embodiments a charging circuit 603 is coupled between thecharging node 120 and the first energy storage device 118 and the secondenergy storage device 119. A power supply (not shown) can be coupled tothe charging node 120 to provide charging current 611 to the chargingcircuit 603, which can feed the charging current 612 to the first energystorage device 118 and charging current 613 to the second energy storagedevice 119, respectively. The charging circuit 603 can include a controlcircuit configured to control the amount of charging current 612,613that flows to the first energy storage device 118 and the second energystorage device 119.

The charging circuit 603 limit current flowing to the first energystorage device 118 and the second energy storage device 119 bycontrolling a current control circuit. The current control circuit ofthe charging circuit 603 can include, for example, a sense resistor607,608, a field effect transistor 614,615, and optionally a diode.These components can be coupled in series in one or more embodiments.The field effect transistors 614,615 can be used to limit, or stop,charging current 612,613 flowing from the charging node 120 to the firstenergy storage device 118 and the second energy storage device 119,respectively, while still allowing load currents to flow from the firstenergy storage device 118 and the second energy storage device 119 tothe load elements 601,602 through the respective parasitic diode. Thecontrol circuit of the charging circuit 603 can use, as inputs,connections disposed on either side of the sense resistor 607,608, aswell as inputs from the various fuel gauge circuits 604,605,66.

Data can be transferred between the control circuit of the chargingcircuit 603 and the memory (113) of the electronic device (100) for usein controlling the current control circuit. Examples of such datainclude rated charging limit of the first energy storage device 118 andthe second energy storage device 119, rated discharging limit of thefirst energy storage device 118 and the second energy storage device119, type of cell of each of the first energy storage device 118 and thesecond energy storage device 119, characteristic cell voltagescorresponding to capacity thresholds of the first energy storage device118 and the second energy storage device 119, and so forth. Otherinformation useful for controlling the charge and discharge of the firstenergy storage device 118 and the second energy storage device 119 willbe obvious to those of ordinary skill in the art having the benefit ofthis disclosure.

In operation, when a power supply is coupled to the charging node 120,charging current 611 can flow from the power supply to the first energystorage device 118 and the second energy storage device 119 to chargethe first energy storage device 118 and the second energy storage device119 from their discharge voltage limit to the rated charging limit. Thecharging circuit 603 can monitor the charging current 612,613 that isbeing transferred to the first energy storage device 118 and/or thesecond energy storage device 119 using one or more fuel gauge circuits604,605,606 and/or current sense resistors 607,608. During the chargingprocess, the charging circuit 603 can also monitor the temperature ofthe first energy storage device 118 and the second energy storage device119 using a thermistor or other temperature measurement device. If thetemperature rises above a predetermined threshold, the charging circuit603 can adjust the flow of charging current 612,613 accordingly.

Each of the first energy storage device 118 and the second energystorage device 119 can have associated therewith an overprotectioncircuit 609,610. Each overprotection circuit 609,610 can monitor thecharging current 612,613 to, and voltage of, the first energy storagedevice 118 and the second energy storage device 119, The overprotectioncircuit 609,610 can additionally (and optionally) control the chargingand discharging of the first energy storage device 118 and the secondenergy storage device 119 in one or more embodiments.

Illustrating by example, the overprotection circuits 609,610 can includean overcharge detector that monitors the voltages across thecorresponding energy storage device. The overcharge detector can thencomparee these voltages to a predetermined maximum energy storage devicevoltage. When the energy storage device voltage exceeds this threshold,the overcharge detector, via some internal logic circuitry, can actuatea charge interrupt device, such as a transistor, to prevent any furthercharging of the first energy storage device 118 or the second energystorage device 119.

Similarly, overprotection circuits 609,610 can include an over dischargedetector that ensures that the voltage across the first energy storagedevice 118 and second energy storage device 119 does not fall below apredetermined threshold. If it does, the over discharge detector canopen to a disconnect device such as a serial transistor to prevent anyfurther discharge of the cells.

In the illustrative embodiment of FIG. 6, the first energy storagedevice 118 and the second energy storage device 119 are coupled inparallel by the flexible substrate 502. This allows allowing the firstenergy storage device 118 and the second energy storage device 119 tofunction within the electronic device (100) effectively as a singleenergy storage device with a doubled current capacity.

As noted above with reference to FIG. 5, in one or more embodiments theflexible substrate 502 spans the hinge (101) of the electronic device(100). The flexible substrate 502 then bends and deforms as the firstdevice housing (102) pivots about the hinge (101) relative to the seconddevice housing (103) between the axially displaced open position (400)and the closed position (200). Due to the mechanical limitations ofthese dynamic requirements of the flexible substrate 502, which includelimitations upon conductor thickness, number of layers of substrate, andso forth, the inherent resistance of the electrical conductors of theflexible substrate 502 becomes non-trivial. Moreover, due to themechanical limitations imposed by some applications, it is frequentlythe case that this impedance cannot easily be lowered. In someinstances, the impedance introduced between the first energy storagedevice 118 and the second energy storage device 119 can be on the orderof one hundred milli-Ohms or more.

Embodiments of the disclosure contemplate that this impedance can have asignificant and deleterious effect on the amount of time it takes tocharge each of the first energy storage device 118 and the second energystorage device 119. Consider the situation where the charging current611 passing through the charging circuit 603 is split into a firstenergy storage device charge current 612 and a second energy storagedevice charge current 613. Applying Kirchhoff's Circuit Laws and Ohm'sLaw results in the following equations (ESD1 is shorthand for firstenergy storage device, while ESD2 is shorthand for second energy storagedevice):

I _(CHARGE_TOTAL) =I _(CHARGE_ESD1) +I _(CHARGE_ESD2)  (EQ. 1)

V _(FLEX) =I _(CHARGE_ESD2) ×R _(FLEXIBLE_SUBSTRATE)  (EQ. 2)

V _(FLEXIBLE_SUBSTRATE) =V _(ESD1) −V _(ESD2)  (EQ. 3)

I _(CHARGE_ESD2)=[V _(ESD1) V _(ESD2)]/R _(FLEXIBLE_SUBSTRATE)  (EQ. 4)

Now consider the situation where first energy storage device 118 andsecond energy storage device 119 are in a quiescent state and are at thesame voltage, e.g., 4.0 volts, when a power supply is coupled to thecharging node 120. Also assume that the impedance of the flexiblesubstrate 502 is one hundred milli-Ohms. If the total charging current611 is two amperes, substituting these values into EQ. 1 and EQ. 4 aboveresults in the following equations:

I _(CHARGE_ESD2)=[V _(ESD1) −V _(ESD2)]/R_(FLEXIBLE_SUBSTRATE)=[4V−4V]/0.1Ω=0.0 A  (EQ. 5)

And

I _(CHARGE_ESD1) =I _(CHARGE_TOTAL) −I _(CHARGE_ESD2)=2.0−0.0=2.0A  (EQ. 6)

As shown in EQS. 5 and 6, all of the charge current initially goes intothe first energy storage device 118 and none gets to the second energystorage device 119 (at least momentarily). Of course, the voltages ofthe first energy storage device 118 and the second energy storage device119 do not remain at exactly 4.0 volts for long once charging commences.Once the first energy storage device 118 starts to charge, its voltagewill rise. Assume for the moment that the voltage of the first energystorage device 118 increases 50 milli-volts while the second energystorage device 119 remains at its original voltage of 4.0 volts. (Notethat this does not really happen, as a very small portion of the chargecurrent would begin to flow into the second energy storage device 119,allowing it to charge very slightly. However, for the purpose ofillustration, this fact can be ignored for the moment). The followingequations would result:

I _(CHARGE_ESD2)=[V _(ESD1) −V _(ESD2)]/R_(FLEXIBLE_SUBSTRATE)=[4.05V−4V]/0.1Ω=0.5 A  (EQ. 7)

And

I _(CHARGE_ESD1) =I _(CHARGE_TOTAL) −I _(CHARGE_ESD1)=2.0−0.5=1.5A  (EQ. 8)

By comparing EQ. 7 with EQ. 5, it can be seen that the current enteringthe second energy storage device 119 is becoming significant. Thiscurrent will continue to increase as the difference between the voltagesof the first energy storage device 118 and the second energy storagedevice 119 increases. Moreover, this trend will continue as the voltageof the first energy storage device 118 rises and levels off at itsterminal voltage, which may be 4.45 volts or similar. This has theeffect of decreasing the current that the first energy storage device118 can accept. At some point in this process, the current into thesecond energy storage device 119 will increase above that entering thefirst energy storage device 118. By the end of the constant currentportion of the charge curve, both the first energy storage device 118and the second energy storage device 119 will be at or close to theirterminal voltage and will then go into the constant voltage phase.

This operation expressed by EQS. 1-8 deleteriously affects overallcharging time. To understand this, consider the charging constraintsfrom the perspective of the first energy storage device 118 and thesecond energy storage device 119. Each energy storage device has amaximum charge current rating, which is specified by the manufacturerand is determined by the chemistry and internal structure of the energystorage device. In one or more embodiments, each of the first energystorage device 118 and the second energy storage device 119 are ratedfor a “1C” charge rate, where a “C” rate is the current (in or out) as aratio of the charge or discharge current to the full capacity of thefirst energy storage device 118 or second energy storage device 119 inmilli-amp-hours.

Thus, a “1C” rate of a 2000 milli-amp-hours energy storage device is2000 milli-amps. If the charge current limit of the second energystorage device 119 is 1.50 amps, while the charge current limit for thefirst energy storage device 118 is 1.217 amps, these numbers representthe maximum current each energy storage device can safely accept andmust be followed. However, in FIG. 6 there is only one charging circuit603 limiting the total charging current 611 into the system. Thischarging circuit 603 must therefore limit the total charging current 611such that neither limit is exceeded. The net effect is that a lowertotal charge current is necessary, resulting in longer charge time.

Turning now to FIG. 8, illustrated therein is an alternate schematicdiagram 800 that eliminates the deleterious charging effects caused bythe inherent impedance of the flexible substrate (502) and circuitconfiguration of FIG. 6. The schematic diagram 800 of FIG. 8 includes atleast one additional switch 801 that a control circuit 124 can controlto electrically separate the first energy storage device 118 and thesecond energy storage device 119 while each is charging. The schematicdiagram 800 also employs two charging circuits 802,803 to control thecharging current 612,613 flowing into each of the first energy storagedevice 118 and the second energy storage device 119. This is in contrastto the single charging circuit (603) used in FIG. 6. In this way,charging current 612,613 flowing into each of the first energy storagedevice 118 and the second energy storage device 119 can be uniquelytailored to its manufacturer-specified limit.

Once charging is complete, e.g., when a power supply is disconnectedfrom the charging node 120 or energy storage in the first energy storagedevice 118 and the second energy storage device 119 is maximized, thecontrol circuit 124 (or alternatively the charging circuits 802,803 oranother control circuit or processor set) can measure the voltage ofeach of the first energy storage device 118 and the second energystorage device 119 to ensure each is at a similar voltage level. If not,in one or more embodiments a current limiting conductor 804 coupled inparallel with the switch 801 allows the voltages of the first energystorage device 118 and the second energy storage device 119 to equalize.Once these voltages are within a predefined voltage differencethreshold, the control circuit 124 can close the switch 801 toreestablish the electrical path coupling the first energy storage device118 and the second energy storage device 119 in parallel to allow normaldischarge into the load elements to resume.

In the schematic diagram 800 of FIG. 8, the first energy storage device118 is coupled to the second energy storage device by a conductor 805 ofthe flexible substrate 502. A charging node 120 is operatively coupledto the first energy storage device 118. In contrast to the schematicdiagram (600) of FIG. 6, in FIG. 8 another conductor 806 of the flexiblesubstrate then operatively couples the charging node 120 to the secondenergy storage device 119.

As shown in FIG. 8, a first charging circuit 802 is coupled between thecharging node 120 and the first energy storage device 118. Similarly, asecond charging control circuit 803 is coupled between the otherconductor 806 and the second energy storage device 119. These chargingcontrol circuits 802,803 can independently control the charge current612,613 flowing into the first energy storage device 118 and the secondenergy storage device 119 using field effect transistors 614,615 aspreviously described.

A switch 801 is then electrically coupled between the conductor 805 andthe second energy storage device 119. A control circuit 124 opens theswitch 801 when a difference between a voltage of the first energystorage device 118 and a voltage of the second energy storage device 119exceeds a predefined voltage difference threshold. The control circuit124 closes the switch 801 when the voltage of the first energy storagedevice 118 and the voltage of the second energy storage device 119 arewithin the predefined voltage difference threshold.

The predefined voltage difference threshold will be different fordifferent energy storage devices, and will depend upon a variety offactors, including the internal impedances of the first energy storagedevice 118 and the second energy storage device 119, the impedance ofthe conductor 805 of the flexible substrate 502, and the impedance ofthe corresponding return conductor 807, in addition to other factors. Inone or more embodiments, the predefined voltage difference threshold is10 milli-volts. In another embodiment, the predefined voltage differencethreshold is 25 milli-volts. In still another embodiment, the predefinedvoltage difference threshold is 50 milli-volts. In yet anotherembodiment, the predefined voltage difference threshold is 0.1 volts.Other examples of predefined voltage difference thresholds will beobvious to those of ordinary skill in the art having the benefit of thisdisclosure.

In the illustrative embodiment of FIG. 8, a current limiting conductor804 is coupled in parallel with the switch 801. The current limitingconductor 804 allows balancing of the voltages of the first energystorage device 118 and the second energy storage device 119 by allowinga trickle current to flow around the switch 801.

The current limiting conductor 804 can take different forms. In one ormore embodiments, the current limiting conductor 804 simply comprises aresistor 808 coupled in parallel with the switch 801. In theillustrative embodiment of FIG. 8, to allow for selective control of thebalancing of the voltages of the first energy storage device 118 and thesecond energy storage device 119, the current limiting conductor 804comprises a resistor 808 coupled in series with another switch 809, withthat serial resistor—other switch combination being coupled in parallelwith the switch 801. Accordingly, in some embodiments the other switch809 will be included to allow for the control of current flowing throughthe current limiting conductor 804, while in other embodiments the otherswitch 809 will be omitted.

Where the other switch 809 is included, the control circuit 124 closesthe other switch when the difference between the voltage of the firstenergy storage device 118 and the voltage of the second energy storagedevice 119 exceeds the predefined voltage difference threshold in one ormore embodiments. In one or more embodiments, the control circuit 124only closes the other switch when the difference between the voltage ofthe first energy storage device 118 and the voltage of the second energystorage device 119 exceeds the predefined voltage difference thresholdand the switch 801 is open.

The control circuit 124 can then optionally open the other switch 809when the difference between the voltage of the first energy storagedevice 118 and the voltage of the second energy storage device 119 fallswithin the predefined voltage difference threshold. However, where thecontrol circuit 124 closes the switch 801 in response to the voltage ofthe first energy storage device 118 and the voltage of the second energystorage device 119 falling within the predefined voltage differencethreshold, this provides a low impedance path in parallel to the currentlimiting conductor 804, thereby effectively taking it out of thecircuit. Accordingly, in some embodiments after opening the other switch809 when the difference between the voltage of the first energy storagedevice 118 and the voltage of the second energy storage device 119exceeds the predefined voltage difference threshold, the control circuit124 may simply allow the other switch 809 to remain closed when thevoltage of the first energy storage device 118 and the voltage of thesecond energy storage device 119 falls back within the predefinedvoltage difference threshold.

In one or more embodiments, where the schematic diagram 800 is used inan electronic device configured as was the electronic device (100) ofFIG. 1, i.e., with a first device housing 102 coupled to a second devicehousing 103 by a hinge 101, the first energy storage device 118 can besituated within the first device housing 102, while the second energystorage device 119 is situated in the second device housing 103. Thisconfiguration is shown in FIG. 8. Since the flexible substrate 502 spansthe hinge 101, this results in the conductor 805 and the other conductor806, as well as the return conductor 807, spanning the hinge 101 aswell.

Embodiments of the disclosure contemplate that the conductor 805, theother conductor 806, and the return conductor 807 frequently will haveto share real estate with other conductors along the flexible substrate502. Illustrating by example, data conductors, signal conductors, andother conductors will generally also be included along the flexiblesubstrate 502 to connect the circuit components of load element 601 toload element 602. Accordingly, design limitations may indeed be placedupon the amount of area of the flexible substrate 502 that the conductor805, the other conductor 806, and the return conductor 807 can occupy.

With this in mind, embodiments of the disclosure contemplate that theimpedances of each of the conductor 805, the other conductor 806, andthe return conductor 807 can be different without sacrificingperformance. For instance, in one or more embodiments the returnconductor 807 has the lowest impedance of the three, as it defines aground node for the schematic diagram 800. In one or more embodiments,the conductor 805 then has the next lowest impedance, since it defines aVcc node for load element 601 and load element 602 in the schematicdiagram 800. Where limitations have to be imposed, conductor 806 canthen have the highest impedance of the three, as it is used only whencharging the second energy storage device 119. Accordingly, in one ormore embodiments the conductor 805 has a predefined impedance, while theother conductor 806 has an impedance that is greater than the predefinedimpedance.

Turning now to FIG. 7, illustrated therein is one explanatory flexiblesubstrate 700 configured in this manner. One or more layers ofinsulative material 701 encapsulate one or more conductive electricaltraces 702 in a sandwiched format. In one embodiment, the one or morelayers of insulative material 701 encapsulate a single layer of one ormore conductive electrical traces 702 in a sandwiched format. However,in other embodiments, the one or more layers of insulative material 701will include a plurality of layers of insulative material so as toencapsulate multiple layers of conductive electrical traces. Otherconfigurations for the flexible substrate 700 will be obvious to thoseof ordinary skill in the art having the benefit of this disclosure.

In one or more embodiments, one or more conductive electrical pads703,704 can be exposed in the insulative material 701 and can be coupledelectrically by the one or more conductive electrical traces 702. Theflexible substrate 700 can include one or more apertures 705,706 orother mechanical features that allow the first end 707 and second end708 of the flexible substrate 700 to be anchored within a devicehousing.

In this illustrative embodiment, the flexible substrate 700 isconfigured as a double-tapering polygon having a length of betweenseventy-three millimeters and seventy-four millimeters, and a width ofabout twenty-seven millimeters. The first end 707 and the second end 708are narrower than is the movable region that spans the hinge (101) of anelectronic device (100). In this embodiment, the movable region has alength of between fifty-one and fifty-two millimeters. Thedouble-tapering polygon includes a generally rectangular shape for themovable region, bounded at each end by a frustoconical tapering portion.The frustoconical tapering portions are then bounded by the generallyrectangular first end 707 and second end 708. This double-taperingpolygon illustrates the fact that flexible substrates configured inaccordance with embodiments of the disclosure can be configured in avariety of different shapes.

As shown in FIG. 7, the one or more electrical traces 702 include thereturn conductor 807, the conductor 805, and the other conductor 806. Inthis illustrative embodiment, the return conductor 807 includes thelargest amount of conductive material, and thus has the lowest impedanceof the three. The conductor 805 has more conductive material than doesthe other conductor 806, giving it a predefined impedance that is lessthan that of the other conductor 806. The printed trace configurationsshown in FIG. 7 are illustrative only, as others will be obvious tothose of ordinary skill in the art having the benefit of thisdisclosure. However, they demonstrate how in one or more embodimentswhere the conductor 805 has a predefined impedance, the other conductor806 can have another predefined impedance that is greater than thepredefined impedance of the conductor 805.

Turning now to FIG. 9, illustrated therein is one explanatory method 900of using the schematic diagram (800) of FIG. 8 in accordance with one ormore embodiments of the disclosure. The method 900 includes opening aswitch (801) coupled between a first energy storage device (118) and anelectrical conductor (805) coupling the switch (801) to a second energystorage device (119) when a difference between a voltage of the firstenergy storage device (118) and a voltage of the second energy storagedevice (119) exceeds a predefined voltage difference threshold, therebyallowing a first charging current (612) to flow from a charging node(120) to the first energy storage device (118) through the electricalconductor (805) and a second charging current (613) to flow from thecharging node (1200 to the second energy storage device (119) throughthe other conductor (806). The method 900 then closes the switch (801)when the difference between the voltage of the first energy storagedevice (118) and the voltage of the second energy storage device (119)is within the predefined voltage difference threshold to electricallycouple the first energy storage device (118) to the second energystorage device (119) with the electrical conductor (805).

It should be noted that the method 900 can begin with the currentlimiting conductor (804) in differing configurations. Recall from abovethat in one embodiment, the current limiting conductor (804) comprisesonly a current limiting resistor (808), with the other switch (809)omitted from the schematic diagram (800). This is one possibleconfiguration. In another configuration, the other switch (809) isincluded and is open when the method 900 begins. In still anotherconfiguration, the other switch (809) is included and is closed when themethod 900 begins.

At decision 901, the method 900 determines whether a power supply iscoupled to the charging node (120). Where it is, the method proceeds todecision 902. Where it is not, the method 900 waits for a power supplyto be coupled to the charging node (120) in one or more embodiments.

At decision 902, the method 900 determines whether either of the firstenergy storage device (118) or the second energy storage device (119)has been depleted below a minimum energy storage threshold. Effectively,decision 902 determines whether either of the first energy storagedevice (118) or the second energy storage device (119) is “dead.” Recallfrom above that in operation, when a power supply is coupled to thecharging node (120) the charging circuits (802,803) can deliver chargingcurrent (612,613) from the power supply to the first energy storagedevice (118) and the second energy storage device (119) to charge thefirst energy storage device (118) and the second energy storage device(119) from their discharge voltage limit to the rated charging limit.Decision 902 determines whether the first energy storage device (118)and the second energy storage device (119) have somehow been depletedbelow their discharge voltage limit. Where they have, a recovery processbegins at step 903. Otherwise, the method 900 proceeds to step 907 wherea standard charging process begins.

At step 904, the switch (801) is opened. At step 905, the chargingcircuits (802,803) begin a trickle charging process to deliver a smallcurrent to one or both of the first energy storage device (118) and/orthe second energy storage device (119) to slowly bring their voltages,and thus stored energy amount, back to the discharge voltage limit.Decision 906 determines whether this occurs, and the process can repeatuntil the first energy storage device (118) and the second energystorage device (119) are both above the discharge voltage limit.

The standard charging process then begins at step 907. In one or moreembodiments, step 908 comprises opening the switch (801) coupled betweenthe first energy storage device (118) and the electrical conductor (805)coupling the switch (801) to the second energy storage device (119),thereby allowing a first charging current (612) to flow from thecharging node (120) to the first energy storage device (118) through theconductor (805) and a second charging current (613) to flow from thecharging node (120) to the second energy storage device (119) throughanother conductor (806) at step 909. In one or more embodiments, step903 occurs in response to a charger or power supply being coupled to thecharging node (120).

Decision 910 determines whether the first energy storage device (118)and the second energy storage device (119) have reached their ratedcharging limit. Where it has not, charging continues with the chargingcurrents (612,613) set for the maximum rated charging current for thefirst energy storage device (118) and second energy storage device(119), respectively, at step 909.

Decision 910 determines whether a difference between the voltage of thefirst energy storage device and the voltage of the second energy storagedevice exceeds a predefined voltage difference threshold. Where it does,and where the other switch (809) is included and is open when the method900 starts, step 912 comprises closing this other switch (809) to allowbalancing of the first energy storage device (118) and the second energystorage device (119). Said differently, in one or more embodiments step912 comprises coupling a current limiting conductor (804) in parallelwith the switch (801). Step 913, which can precede step 912, ensuresthat the switch (801) is open while this balancing occurs. Accordingly,in one or more embodiments step 912 occurs while the difference betweenthe voltage of the first energy storage device (118) and the secondenergy storage device (119) exceeds the predefined voltage differencethreshold and the switch (801) is open. In one or more embodiments, step912 closes the other switch (809) with the other switch (809) coupledserially with a resistor (808), thereby defining the current limitingconductor (804).

When the difference between the voltage of the first energy storagedevice (118) and a voltage of the second energy storage device (119)falls within the predefined voltage difference threshold at decision911, step 914 comprises closing the switch (801) so that the firstenergy storage device (118) and the second energy storage device (119),now balanced, can be coupled in parallel to deliver load currents to afirst load element (601) and a second load element (602). Optionally,where the other switch (809) is included and is closed, step 914 cancomprise opening the other switch (809) when the first energy storagedevice (118) and a voltage of the second energy storage device (119)falls within the predefined voltage difference threshold as well.

Turning now to FIG. 10, illustrated therein is another schematic diagram1000 in accordance with one or more embodiments of the disclosure. Thecomponents of the schematic diagram (1000) of FIG. 10 are similar tothose of the schematic diagram (800) of FIG. 8. For instance, anelectronic device (100) includes a first device housing 102 coupled to asecond device housing 103 by a hinge 101. A first energy storage device118 is situated in the first device housing 102, while a second energystorage device 119 is situated in the second device housing 103 andelectrically coupled to the first energy storage device 118 by aconductor 805 spanning the hinge 101.

A charging node 120 at the first device housing 102 is electricallycoupled to the first energy storage device 118. The charging node 120 iselectrically coupled to the second energy storage device 119 by theconductor 805 as well. Additionally, another conductor 807 spans thehinge 101 and also couples the charging node 120 to the second energystorage device 119 as previously described.

A switch 801 is electrically coupled between the conductor 805 spanningthe hinge 101 and the second energy storage device 119. A controlcircuit 124 is then coupled to the switch 801. In one or moreembodiments, the control circuit 124 opens the switch 801 duringcharging, thereby allowing a first charging current 612 to flow from thecharging node 120 to the first energy storage device 118 through theconductor 805 and a second charging current 613 to flow from thecharging node 120 to the second energy storage device 119 through theother conductor 807. Once the charging process is complete, the controlcircuit 124 closes the switch 801 when a difference between a voltage ofthe first energy storage device (118) and a voltage of the second energystorage device (119) is within a predefined voltage differencethreshold.

As before, a current limiting conductor 804 is coupled in parallel withthe switch 801. Here the current limiting conductor 804 comprises aresistor coupled serially with another switch 809. In one or moreembodiments, the control circuit 124 closes the other switch 809 whenthe difference between the voltage of the first energy storage device118 and the voltage of the second energy storage device 119 exceeds thepredefined voltage different threshold. In one or more embodiments, thecontrol circuit 124 closes the other switch 809 only when the switch 801is open.

The schematic diagram 1000 of FIG. 10 differs from the schematic diagram(800) of FIG. 8 in that it includes a combiner 1001 that allows thecharging current 612,613 to be delivered from either the charging node120 or from a wireless charging node 1002. By controlling two switches1003,1004, the schematic diagram 1000 can allow the first energy storagedevice 118 and the second energy storage device 119 to receive chargingcurrent 612,613 from, or deliver load current to, either or both of thecharging node 120 and/or the wireless charging node 1002, with thelatter powering accessory devices coupled to the respective node.

Turning now to FIG. 11, illustrated therein is another explanatorymethod 1100 in accordance with one or more embodiments of thedisclosure. The method 1100 of FIG. 11 could be used with either theschematic diagram (800) of FIG. 8 or the schematic diagram (1000) ofFIG. 10. For simplicity, reference will be made to the schematic diagram(800) of FIG. 8 when describing the method 1100 of FIG. 11. Those ofordinary skill in the art having the benefit of this disclosure willreadily understand from these teachings the application of the method1100 of FIG. 11 to the schematic diagram (1000) of FIG. 10 from theseteachings.

As with the method (900) of FIG. 9, the method 1100 of FIG. 11 includesopening a switch (801) coupled between a first energy storage device(118) and an electrical conductor (805) coupling the switch (801) to asecond energy storage device (119) when a difference between a voltageof the first energy storage device (118) and a voltage of the secondenergy storage device (119) exceeds a predefined voltage differencethreshold. This action allows a first charging current (612) to flowfrom a charging node (120) to the first energy storage device (118)through the electrical conductor (805) and a second charging current(613) to flow from the charging node (1200 to the second energy storagedevice (119) through the other conductor (806). The method 1100 thencloses the switch (801) when the difference between the voltage of thefirst energy storage device (118) and the voltage of the second energystorage device (119) is within the predefined voltage differencethreshold to electrically couple the first energy storage device (118)to the second energy storage device (119) with the electrical conductor(805).

It should be noted that the method 1100 can begin with the currentlimiting conductor (804) in differing configurations. In one or moreembodiments, the state of each of the switch (801) and the other switch(809) is a function of whether the electronic device (100) in which theschematic diagram (800) is operating is ON, e.g., unlocked, active, andusable, or OFF, e.g., in a low-power, sleep, or inactive mode.

In one or more embodiments, when the electronic device (100) in whichthe schematic diagram (800) is operating is OFF, the switch (801) isopen when the method 1100 begins. In one or more embodiments, the otherswitch (809) is closed when the method 1100 begins and the electronicdevice (100) in which the schematic diagram (800) is operating is OFF.

In one or more embodiments, when the electronic device (100) in whichthe schematic diagram (800) is operating is ON, the other switch (809)is closed when the method 1100 begins. In one or more embodiments, whenthe electronic device (100) in which the schematic diagram (800) isoperating is ON, the state of the switch (801) can be either open orclosed depending upon the state of charge of each of the first energystorage device (118) and the second energy storage device (119).Illustrating by example, in one embodiment where the difference in thevoltage of the first energy storage device (118) or the second energystorage device (119) is within a predefined difference threshold and theelectronic device (100) is ON, the switch 801 is closed when the method1100 begins. However, where the difference in the voltage of the firstenergy storage device (118) or the second energy storage device (119)exceeds the predefined difference threshold and the electronic device(100) is ON, the switch 801 is open when the method 1100 begins.

In other embodiments, such as where the current limiting conductor (804)comprises only a current limiting resistor (808), with the other switch(809) omitted from the schematic diagram (800), the switch (801) will beopen when the method 1100 begins and the electronic device (100) is OFF.Of course, both the switch (801) and the other switch (809) can be openwhen the method 1100 begins as well.

Decision 1101 determines whether a difference between the voltage of thefirst energy storage device (118) and the voltage of the second energystorage device (119) is within a predefined voltage differencethreshold. In one or more embodiments, the predefined voltage differencethreshold is 10 milli-volts. In another embodiment, the predefinedvoltage difference threshold is 25 milli-volts. In still anotherembodiment, the predefined voltage difference threshold is 50milli-volts. In yet another embodiment, the predefined voltagedifference threshold is 0.1 volts. Other examples of predefined voltagedifference thresholds will be obvious to those of ordinary skill in theart having the benefit of this disclosure.

Where it is, step 1103 comprises closing the switch (801) to bypass thecurrent limiting conductor (804) coupled in parallel with the switch(801) via the fact that the other switch (809) is closed. Saiddifferently, when the difference between the voltage of the first energystorage device (118) and a voltage of the second energy storage device(119) falls within the predefined voltage difference threshold atdecision 1101, step 1103 comprises closing the switch (801) so that thefirst energy storage device (118) and the second energy storage device(119), which are in balance, are be coupled in parallel so as to be ableto deliver load currents to a first load element (601) and a second loadelement (602). The method 1100 then moves to decision 1102.

Where decision 1101 determines that difference between the voltage ofthe first energy storage device (118) and the voltage of the secondenergy storage device (119) exceeds the predefined voltage differencethreshold, the method 1100 also moves to decision 1102. At decision1102, the method 1100 determines whether a power supply is coupled tothe charging node (120). Where it is, the method proceeds to decision1104. Where it is not, the method 900 waits for a power supply to becoupled to the charging node (120) in one or more embodiments.

At decision 1104, the method 1100 determines whether either of the firstenergy storage device (118) or the second energy storage device (119)has been depleted below a minimum energy storage threshold. Saiddifferently, decision 1104 determines whether either of the first energystorage device (118) or the second energy storage device (119) is“dead.” When a power supply is coupled to the charging node (120) thecharging circuits (802,803) can deliver charging current (612,613) fromthe power supply to the first energy storage device (118) and the secondenergy storage device (119) to charge the first energy storage device(118) and the second energy storage device (119) from their dischargevoltage limit to the rated charging limit. Decision 1104 determineswhether the first energy storage device (118) and the second energystorage device (119) have been depleted below their discharge voltagelimit. Where they have, a recovery process begins at step 1105.Otherwise, the method 1100 proceeds to step 1107 where a standardcharging process begins.

At step 1106, the charging circuits (802,803) begin a trickle chargingprocess to deliver a small current to one or both of the first energystorage device (118) and/or the second energy storage device (119) toslowly bring their voltages, and thus stored energy amount, back to thedischarge voltage limit. Decision 1108 determines whether this occurs,and the process can repeat until the first energy storage device (118)and the second energy storage device (119) are both above the dischargevoltage limit, one example of which is 2.1 volts for a single-cell,lithium based battery.

Step 1109 begins a pre-charge process. At step 1109, charging circuit(802) sets a first charging current (612) to a predefined pre-chargecurrent limit, such as 450 milli-Amps to slowly bring the voltage of thefirst energy storage device (118) to a predefined threshold at which itcan be charged with a higher current, one example of which is 2.8 volts.Decision 1110 then determines whether a difference between the voltageof the first energy storage device (118) and the voltage of the secondenergy storage device (119) is within the predefined voltage differencethreshold. Where it is, the method moves to step 1111, where the switch(801) is closed. Otherwise, the pre-charge current continues to bedelivered to the first energy storage device (118).

Decision 1112 then determines whether the voltage of the first energystorage device (118) is above a predefined voltage limit, one example ofwhich is 2.8 volts. Where it is not, the pre-charge current continues tobe delivered to the first energy storage device (118). However, where itis, the method 1100 moves to step 1107.

Step 1107 identifies the type of power supply coupled to the chargingnode (120). Embodiments of the disclosure contemplate that some powersupplies are configured to deliver larger amounts of current thanothers. Illustrating by example, some power supplies are considered“weak” chargers because they deliver a total current of one Amp or less.By contrast, other power supplies are considered “strong” power suppliesbecause they are capable of delivering more than one Amp, and in someembodiments between one Amp and three Amps. Accordingly, in one or moreembodiments step 1107 comprises identifying the type of power supplycoupled to the charging node (120), with decision 1113 determiningwhether the power supply coupled to the charging node (120) is a strongpower supply or a weak power supply.

Where the power supply coupled to the charging node (120) is a weakcharger, a charging process using the less than one Amp of current beingdelivered to the charging node (120) commences at step 1114. Both theswitch (801) and the other switch (809) are closed at step 1115. Thisallows charging circuit (802) to charge both the first energy storagedevice (118) and the second energy storage device (119).

Step 1117 includes adjusting the charging circuit (802) such that thesum of the first charging current (612) and the second charging current(613) to a limit set forth by the following equation:

I _(CHARGE_ESD1_ESD2) =CAP _(ESD1) /CAP _(ESD1_ESD2)*(I _(CHARGE_MAX) −I_(CHARGE_LOAD601+LOAD602))+I _(CHARGE_LOAD601)  (EQ. 9)

where “CAP” refers to the energy storage capacity of the indicatedenergy storage device. Decision 1118 then determines whether the stateof charge, represented in milli-Amp-hours, of the first energy storagedevice (118) and the second energy storage device (119) exceeds apredefined state of charge limit, one example of which is fifteenmilli-Amp-hours. Were it does, i.e., where there is a sufficientmismatch in the state of charge of the first energy storage device (118)and the second energy storage device (119), the process of adjusting thecharging circuit (802) such that the sum of the first charging current(612) and the second charging current (613) to a limit set forth by EQ.9 is repeated at step 1119 as the state of charge of the first energystorage device (118) and the second energy storage device (119)continues to increase.

Once the state of charge of the first energy storage device (118) andthe second energy storage device (119) falls within the predefined stateof charge limit, decision 1120 determines whether the first energystorage device (118) and the second energy storage device (119) havereached their rated charging limit. Where it has not, charging continueswith the charging currents (612,613) set in accordance with EQ. 9 aboveat step 1119. Otherwise, the method 1100 ends.

Had the power supply coupled to the charging node (120) been determinedto be a strong charger at decision 1113, the method would have proceededto step 1116, where a fast charging process could commence. Step 1121would then open the switch (801) and the other switch (902), therebyallowing a first charging current (612) to flow from the charging node(120) to the first energy storage device (118) through the conductor(805) and a second charging current (613) to flow from the charging node(120) to the second energy storage device (119) through anotherconductor (806).

Since two charging circuits (802,803) are charging the first energystorage device (118) and the second energy storage device (119) in thiscondition, step 1122 then sets the first charging current (612) and thesecond charging current (613). The first charging current (612) is setin accordance with EQ. 9 above. To wit, step 1122 adjusts the firstcharging circuit (802) such that the first charging current (612) is setto a limit set forth by EQ. 9. Similarly, step 1122 adjusts the secondcharging circuit (803) such that the second charging current is set to alimit set forth by the following equation:

I _(CHARGE_ESD1_ESD2) =CAP _(ESD2) /CAP _(ESD1_ESD2)*(I _(CHARGE_MAX) −I_(CHARGE_LOAD601+LOAD602))+I _(CHARGE_LOAD602)  (EQ. 10)

Decision 1123 then determines whether the state of charge, representedin milli-Amp-hours, of the first energy storage device (118) and thesecond energy storage device (119) exceeds a predefined state of chargelimit, one example of which is fifteen milli-Amp-hours. Were it does,i.e., where there is a sufficient mismatch in the state of charge of thefirst energy storage device (118) and the second energy storage device(119), the process of adjusting the charging circuit (802) such that thefirst charging current (612) is limited by EQ. 9 and the second chargingcurrent (613) is limited by EQ. 10 is repeated at step 1124 as the stateof charge of the first energy storage device (118) and the second energystorage device (119) continues to increase.

Once the state of charge of the first energy storage device (118) andthe second energy storage device (119) falls within the predefined stateof charge limit, decision 1125 determines whether the first energystorage device (118) and the second energy storage device (119) havereached their rated charging limit. Where it has not, charging continueswith the charging currents (612,613) set in accordance with EQ. 9 aboveat step 1119. Otherwise, the switch (801) and the other switch (809) areclosed at step 1126 and the method 1100 ends.

Turning now to FIG. 12, illustrated therein are various embodiments ofthe disclosure. The embodiments of FIG. 12 are shown as labeled boxes inFIG. 12 due to the fact that the individual components of theseembodiments have been illustrated in detail in FIGS. 1-11, which precedeFIG. 12. Accordingly, since these items have previously been illustratedand described, their repeated illustration is no longer essential for aproper understanding of these embodiments. Thus, the embodiments areshown as labeled boxes.

At 1201, an electronic device comprises a first energy storage devicecoupled to a second energy storage device by a conductor. At 1201, theelectronic device comprises a charging node coupled to the first energystorage device.

At 1201, the electronic device comprises another conductor coupling thecharging node to the second energy storage device. At 1201, theelectronic device comprises a switch electrically coupled between theconductor and the second energy storage device.

At 1201, a control circuit opens the switch when a difference between avoltage of the first energy storage device and a voltage of the secondenergy storage device exceeds a predefined voltage difference threshold.At 1201, the control circuit closes the switch when the differencebetween the voltage of the first energy storage device and the voltageof the second energy storage device is within the predefined voltagedifference threshold.

At 1202, the electronic device of 1201 further comprises a currentlimiting conductor coupled in parallel with the switch. At 1203, thecurrent limiting conductor of 1202 comprises a resistor coupled inparallel with the switch. At 1204, the current limiting conductor of1202 comprises a resistor coupled in series with another switch.

At 1205, the control circuit of 1204 closes the other switch when thedifference between the voltage of the first energy storage device andthe voltage of the second energy storage device exceeds the predefinedvoltage difference threshold. At 1206, the control circuit of 1205closes the other switch only when both the difference between thevoltage of the first energy storage device and the voltage of the secondenergy storage device exceeds the predefined voltage differencethreshold and the switch is open.

At 1207, the electronic device of 1201 further comprises a first devicehousing coupled to a second device housing by a hinge, with the firstenergy storage device situated within the first device housing, thesecond energy storage device situated within the second device housing,and the conductor and the other conductor spanning the hinge. At 1208,the conductor of 1207 has a predefined impedance, and the otherconductor has another predefined impedance that is greater than thepredefined impedance.

At 1209, the electronic device of 1201 further comprises a firstcharging control circuit coupled between the charging node and the firstenergy storage device and a second charging control circuit coupledbetween the other conductor and the second energy storage device. At1210, the electronic device of 1209 further comprises a wirelesscharging terminal coupled to both the first charging control circuit andthe other conductor.

At 1211, a method in an electronic device comprises opening a switchcoupled between a first energy storage device and an electricalconductor coupling the switch to a second energy storage device when adifference between a voltage of the first energy storage device and avoltage of the second energy storage device exceeds a predefined voltagedifference threshold, thereby allowing a first charging current to flowfrom a charging node to the first energy storage device through theelectrical conductor and a second charging current to flow from thecharging node to the second energy storage device through anotherelectrical conductor. At 1211, the method comprises closing the switchwhen the difference between the voltage of the first energy storagedevice and the voltage of the second energy storage device is within thepredefined voltage difference threshold to electrically couple the firstenergy storage device to the second energy storage device with theelectrical conductor.

At 1212, the method of 1211 further comprises coupling a currentlimiting conductor in parallel with the switch while the differencebetween the voltage of the first energy storage device and the voltageof the second energy storage device exceeds the predefined voltagedifference threshold and the switch is open. At 1213, the coupling of1212 comprises closing another switch serially coupled with a resistor,with the other switch and the resistor defining the current limitingconductor. At 1214, the opening of the switch at 1211 occurs in responseto a charger being connected to the charging node.

At 1215, an electronic device comprises a first device housing coupledto a second device housing by a hinge. At 1215, the electronic devicecomprises a first energy storage device situated in the first devicehousing and a second energy storage device situated in the second devicehousing and electrically coupled to the first energy storage device by aconductor spanning the hinge.

At 1215, the electronic device comprises a charging node at the firstdevice housing that is electrically coupled to the first energy storagedevice. At 1215, the charging node is electrically coupled to the secondenergy storage device by the conductor spanning the hinge.

At 1215, the electronic device comprises another conductor spanning thehinge and also coupling the charging node to the second energy storagedevice. At 1215, the electronic device comprises a switch electricallycoupled between the conductor spanning the hinge and the second energystorage device.

At 1215, the electronic device comprises a control circuit coupled tothe switch. At 1215, the control circuit opens the switch, therebyallowing a first charging current to flow from the charging node to thefirst energy storage device through the conductor and a second chargingcurrent to flow from the charging node to the second energy storagedevice through the other conductor. At 1215, the control circuit closesthe switch when a difference between a voltage of the first energystorage device and a voltage of the second energy storage device iswithin a predefined voltage difference threshold.

At 1216, the electronic device of 1215 further comprises a currentlimiting conductor coupled in parallel with the switch. At 1217, thecurrent limiting conductor of 1216 comprises a resistor serially coupledwith the other switch.

At 1218, the control circuit of 1217 closes the other switch when thedifference between the voltage of the first energy storage device andthe voltage of the second energy storage device exceeds the predefinedvoltage difference threshold. At 1219, the control circuit of 1218closes the other switch only the switch is open. At 1220, the conductorand other conductor of 1215 are physically coupled to a flexiblesubstrate spanning the hinge.

In the foregoing specification, specific embodiments of the presentdisclosure have been described. However, one of ordinary skill in theart appreciates that various modifications and changes can be madewithout departing from the scope of the present disclosure as set forthin the claims below. Thus, while preferred embodiments of the disclosurehave been illustrated and described, it is clear that the disclosure isnot so limited. Numerous modifications, changes, variations,substitutions, and equivalents will occur to those skilled in the artwithout departing from the spirit and scope of the present disclosure asdefined by the following claims.

Accordingly, the specification and figures are to be regarded in anillustrative rather than a restrictive sense, and all such modificationsare intended to be included within the scope of present disclosure. Thebenefits, advantages, solutions to problems, and any element(s) that maycause any benefit, advantage, or solution to occur or become morepronounced are not to be construed as a critical, required, or essentialfeatures or elements of any or all the claims.

What is claimed is:
 1. An electronic device, comprising: a first energystorage device coupled to a second energy storage device by a conductor;a charging node coupled to the first energy storage device; anotherconductor coupling the charging node to the second energy storagedevice; a switch electrically coupled between the conductor and thesecond energy storage device; and a control circuit opening the switchwhen a difference between a voltage of the first energy storage deviceand a voltage of the second energy storage device exceeds a predefinedvoltage difference threshold and closing the switch when the differencebetween the voltage of the first energy storage device and the voltageof the second energy storage device is within the predefined voltagedifference threshold.
 2. The electronic device of claim 1, furthercomprising a current limiting conductor coupled in parallel with theswitch.
 3. The electronic device of claim 2, the current limitingconductor comprising a resistor coupled in parallel with the switch. 4.The electronic device of claim 2, the current limiting conductorcomprising a resistor coupled in series with another switch.
 5. Theelectronic device of claim 4, the control circuit closing the anotherswitch when the difference between the voltage of the first energystorage device and the voltage of the second energy storage deviceexceeds the predefined voltage difference threshold.
 6. The electronicdevice of claim 5, the control circuit closing the another switch onlywhen both the difference between the voltage of the first energy storagedevice and the voltage of the second energy storage device exceeds thepredefined voltage difference threshold and the switch is open.
 7. Theelectronic device of claim 1, further comprising a first device housingcoupled to a second device housing by a hinge, with the first energystorage device situated within the first device housing, the secondenergy storage device situated within the second device housing, and theconductor and the another conductor spanning the hinge.
 8. Theelectronic device of claim 7, the conductor having a predefinedimpedance, the another conductor having another predefined impedancethat is greater than the predefined impedance.
 9. The electronic deviceof claim 1, further comprising a first charging control circuit coupledbetween the charging node and the first energy storage device and asecond charging control circuit coupled between the another conductorand the second energy storage device.
 10. The electronic device of claim9, further comprising a wireless charging terminal coupled to both thefirst charging control circuit and the another conductor.
 11. A methodin an electronic device, the method comprising: opening a switch coupledbetween a first energy storage device and an electrical conductorcoupling the switch to a second energy storage device when a differencebetween a voltage of the first energy storage device and a voltage ofthe second energy storage device exceeds a predefined voltage differencethreshold, thereby allowing a first charging current to flow from acharging node to the first energy storage device through the electricalconductor and a second charging current to flow from the charging nodeto the second energy storage device through another electricalconductor; and closing the switch when the difference between thevoltage of the first energy storage device and the voltage of the secondenergy storage device is within the predefined voltage differencethreshold to electrically couple the first energy storage device to thesecond energy storage device with the electrical conductor.
 12. Themethod of claim 11, further comprising coupling a current limitingconductor in parallel with the switch while the difference between thevoltage of the first energy storage device and the voltage of the secondenergy storage device exceeds the predefined voltage differencethreshold and the switch is open.
 13. The method of claim 12, thecoupling comprising closing another switch serially coupled with aresistor, with the another switch and the resistor defining the currentlimiting conductor.
 14. The method of claim 11, wherein the opening theswitch occurs in response to a charger being connected to the chargingnode.
 15. An electronic device, comprising: a first device housingcoupled to a second device housing by a hinge; a first energy storagedevice situated in the first device housing and a second energy storagedevice situated in the second device housing and electrically coupled tothe first energy storage device by a conductor spanning the hinge; acharging node at the first device housing and electrically coupled tothe first energy storage device, wherein the charging node iselectrically coupled to the second energy storage device by theconductor spanning the hinge; another conductor spanning the hinge andalso coupling the charging node to the second energy storage device; aswitch electrically coupled between the conductor spanning the hinge andthe second energy storage device; and a control circuit coupled to theswitch, the control circuit opening the switch, thereby allowing a firstcharging current to flow from the charging node to the first energystorage device through the conductor and a second charging current toflow from the charging node to the second energy storage device throughthe another conductor, and closing the switch when a difference betweena voltage of the first energy storage device and a voltage of the secondenergy storage device is within a predefined voltage differencethreshold.
 16. The electronic device of claim 15, further comprising acurrent limiting conductor coupled in parallel with the switch.
 17. Theelectronic device of claim 16, the current limiting conductor comprisinga resistor serially coupled with another switch.
 18. The electronicdevice of claim 17, the control circuit closing the another switch whenthe difference between the voltage of the first energy storage deviceand the voltage of the second energy storage device exceeds thepredefined voltage difference threshold.
 19. The electronic device ofclaim 18, the control circuit closing the another switch only the switchis open.
 20. The electronic device of claim 15, wherein the conductorand the another conductor are physically coupled to a flexible substratespanning the hinge.